U.S. patent application number 13/939513 was filed with the patent office on 2014-01-30 for liquid ejection head and method of manufacturing the same.
Invention is credited to Isamu Horiuchi, Ken Ikegame, Takuma Kodoi, Hyou Takahashi, Yasunori Takei, Kenji Yabe.
Application Number | 20140030659 13/939513 |
Document ID | / |
Family ID | 49995225 |
Filed Date | 2014-01-30 |
United States Patent
Application |
20140030659 |
Kind Code |
A1 |
Kodoi; Takuma ; et
al. |
January 30, 2014 |
LIQUID EJECTION HEAD AND METHOD OF MANUFACTURING THE SAME
Abstract
A liquid ejection head is manufactured by forming a dent
representing a substantially spherical profile so as to include a
position for forming an ejection port on a surface of a
photosensitive resin layer, then forming a latent image of the
ejection port in the dent by an exposure treatment using a
projection lens system, and developing the latent image. The center
of the top surface of the latent image is shifted to the incoming
side of the beam of exposure light from the lowest point of the
dent.
Inventors: |
Kodoi; Takuma;
(Kawasaki-shi, JP) ; Takei; Yasunori; (Tokyo,
JP) ; Yabe; Kenji; (Yokohama-shi, JP) ;
Horiuchi; Isamu; (Yokohama-shi, JP) ; Takahashi;
Hyou; (Kunitachi-shi, JP) ; Ikegame; Ken;
(Ebina-shi, JP) |
Family ID: |
49995225 |
Appl. No.: |
13/939513 |
Filed: |
July 11, 2013 |
Current U.S.
Class: |
430/320 |
Current CPC
Class: |
G03F 7/0015 20130101;
G03F 7/0045 20130101; B41J 2/1639 20130101; G03F 7/38 20130101;
G03F 7/203 20130101; G03F 7/0002 20130101; B41J 2/1603 20130101;
B41J 2/1645 20130101; B41J 2/1631 20130101; G03F 7/038
20130101 |
Class at
Publication: |
430/320 |
International
Class: |
G03F 7/00 20060101
G03F007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 25, 2012 |
JP |
2012-164688 |
Claims
1. A method of manufacturing a liquid ejection head by forming an
ejection port forming member for configuring an ejection port for
ejecting liquid by using a photosensitive resin layer on a surface
of a substrate, the method comprising: (1) a step of forming a dent
representing a substantially spherical profile in a region
including the position for forming the ejection port on a surface
of the photosensitive resin layer; (2) a step of forming a latent
image corresponding to the ejection port in the dent by way of an
exposure treatment using a projection lens system; and (3) a step
of producing the ejection port by developing the latent image; the
latent image being formed by a beam of exposure light refracted by
the projection lens system and inclined from the direction
perpendicular to the surface of the substrate in the exposure
treatment in the above-described step (2); the center of a top
surface of the latent image being shifted to the incoming side of
the beam of exposure light from the lowest point of the dent.
2. The method according to claim 1, wherein the top surface of the
latent image is arranged so as to include the lowest point of the
dent.
3. The method according to claim 1, wherein the latent image has a
lateral surface so as to form equal angles with the surface of the
substrate at the transversal opposite ends of the lateral surface
in a cross section taken along a plane that passes through the
center of the top surface of the latent image and the lowest point
of the dent and stands perpendicularly relative to the surface of
the substrate.
4. The method according to claim 1, wherein: the ejection port
forming member has a plurality of ejection ports arranged in a row
so as to respectively correspond to a plurality of ejection energy
generating elements formed in the surface of the substrate; and a
plurality of dents are formed so as to respectively correspond to
the plurality of ejection ports in the step (1); while a plurality
of latent images are formed collectively so as to respectively
correspond to the plurality of ejection ports in the exposure
treatment in the step (2); and the center of the top surface of the
latent image of each of the ejection ports located at and near the
ends of the row of ejection ports is shifted to the incoming side
of the beam of exposure light from the lowest point of the dent to
an extent that corresponds to the incident angle of the beam of
exposure light from the direction perpendicular to the surface of
the substrate.
5. The method according to claim 4, wherein the lowest point of
each of the dents is shifted toward the center of the row of
ejection ports from the center of the corresponding ejection
port.
6. The method according to claim 4, wherein the plurality of
ejection ports have the same positional relationship relative to
the corresponding respective ejection energy generating
elements.
7. The method according to claim 2, wherein the latent image has a
lateral surface so as to form equal angles with the surface of the
substrate at the transversal opposite ends of the lateral surface
in a cross section taken along a plane that passes through the
center of the top surface of the latent image and the lowest point
of the dent and stands perpendicularly relative to the surface of
the substrate.
8. The method according to claim 2, wherein: the ejection port
forming member has a plurality of ejection ports arranged in a row
so as to respectively correspond to a plurality of ejection energy
generating elements formed in the surface of the substrate; and a
plurality of dents are formed so as to respectively correspond to
the plurality of ejection ports in the step (1); while a plurality
of latent images are formed collectively so as to respectively
correspond to the plurality of ejection ports in the exposure
treatment in the step (2); and the center of the top surface of the
latent image of each of the ejection ports located at and near the
ends of the row of ejection ports is shifted to the incoming side
of the beam of exposure light from the lowest point of the dent to
an extent that corresponds to the incident angle of the beam of
exposure light from the direction perpendicular to the surface of
the substrate.
9. The method according to claim 3, wherein the ejection port
forming member has a plurality of ejection ports arranged in a row
so as to respectively correspond to a plurality of ejection energy
generating elements formed in the surface of the substrate; and a
plurality of dents are formed so as to respectively correspond to
the plurality of ejection ports in the step (1); while a plurality
of latent images are formed collectively so as to respectively
correspond to the plurality of ejection ports in the exposure
treatment in the step (2); and the center of the top surface of the
latent image of each of the ejection ports located at and near the
ends of the row of ejection ports is shifted to the incoming side
of the beam of exposure light from the lowest point of the dent to
an extent that corresponds to the incident angle of the beam of
exposure light from the direction perpendicular to the surface of
the substrate.
10. The method according to claim 8, wherein the lowest point of
each of the dents is shifted toward the center of the row of
ejection ports from the center of the corresponding ejection
port.
11. The method according to claim 9, wherein the lowest point of
each of the dents is shifted toward the center of the row of
ejection ports from the center of the corresponding ejection
port.
12. The method according to claim 5, wherein the plurality of
ejection ports have the same positional relationship relative to
the corresponding respective ejection energy generating elements.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of manufacturing a
liquid ejection head.
[0003] 2. Description of the Related Art
[0004] Known liquid ejection heads for ejecting liquid include ink
jet recording heads to be used for ink jet recording systems. Ink
jet recording heads generally include one or more ink channels,
ejection energy generating elements arranged at a part of the ink
channel or each of the ink channels to generate energy for ejecting
ink and minute ink ejection ports for ejecting ink.
[0005] For example, a method as described below is known for
manufacturing such an ink jet recording head. Firstly, a mold of an
ink channel is formed on a substrate, which contains heater
elements formed therein in advance, by means of a photosensitive
material and then a coating resin layer that becomes a channel
forming member is formed to coat the channel mold. Thereafter,
ejection ports are formed in the coating resin layer. Then, a
manufactured ink jet recording head comes out as the photosensitive
material that has been used for the mold is removed. With this
manufacturing method, flow channels, ejection ports and so on can
be formed by way of high precision micro processing steps because a
photolithography technique that is being used in the field of
semiconductors is also employed for the method. This manufacturing
method involves exposure to light by a semiconductor exposure
apparatus that operates as means for setting a photosensitive resin
material. The photosensitive resin material is exposed to light by
way of a reticle having a desired profile and by means of a
semiconductor exposure apparatus. The part of the photosensitive
resin material that is shaded and hence not exposed to light
remains unset and is removed in a subsequent removal step.
[0006] In recent years, there is a tendency of using long chips in
order to realize high-speed printing. There is also a tendency of
exposing collectively a plurality of chips to light from the
viewpoint of reducing the time required for the exposure step. For
these reasons, a pattern is arranged nearly to the limits of the
angle of view of the reticle to be used for the exposure step. If
such is the case, the rays of light that are transmitted through a
portion of the projection lens system representing a large
curvature in a semiconductor exposure apparatus are affected by the
aberrations of the lens to by turn adversely affect the profiles of
the ejection ports. Such a phenomenon occurs because, when the rays
of light coming from the exposure apparatus are so adjusted that
the pattern formed at and near the center of the reticle may be
accurately projected on the resist, the rays of light irradiated
from the semiconductor exposure apparatus are refracted to inward
directions of the lens in regions remote from the center of the
reticle. Differently stated, there arise instances where a pattern
is formed at and near the limits of the angle of view of the
reticle for stepper exposure and the ejection ports 6 that
correspond to the parts exposed to the rays of light that have
passed at and near the limits of the angle of view represent an
outwardly inclined profile (see FIG. 10).
[0007] In view of the above-identified problem, Japanese Patent
Application Laid-Open No. 2001-264637 disclosed means for
correcting the aberrations of the lens of a lens system. The means
lies in an ingeniously devised lens system. With such a means, a
spherical aberration correcting optical system is mounted in the
inside and the spherical aberration is corrected by moving the
movable lens group of the system in the directions of the optical
axis.
SUMMARY OF THE INVENTION
[0008] According to the present invention, there is provided a
method of manufacturing a liquid ejection head by forming an
ejection port forming member for configuring an ejection port for
ejecting liquid by using a photosensitive resin layer on a surface
of a substrate, the method including: (1) a step of forming a dent
representing a substantially spherical profile in a region
including the position for forming the ejection port on a surface
of the photosensitive resin layer; (2) a step of forming a latent
image corresponding to the ejection port in the dent by way of an
exposure treatment using a projection lens system; and (3) a step
of producing the ejection port by developing the latent image; the
latent image being formed by a beam of exposure light refracted by
the projection lens system and inclined from the direction
perpendicular to the surface of the substrate in the exposure
treatment in the above-described step (2); the center of a top
surface of the latent image being shifted to the incoming side of
the beam of exposure light from the lowest point of the dent.
[0009] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1A is a schematic illustration of a step of an
embodiment of manufacturing method according to the present
invention;
[0011] FIGS. 1B, 1C and 1D are schematic cross-sectional views
illustrating the exposure step of an embodiment of manufacturing
method according to the present invention.
[0012] FIGS. 2A, 2B, 2C and 2D are schematic cross-sectional views
illustrating the exposure step of an embodiment of manufacturing
method according to the present invention.
[0013] FIGS. 3A and 3B are schematic cross-sectional views
illustrating the exposure step of an embodiment of manufacturing
method according to the present invention.
[0014] FIG. 4 schematically illustrates exemplary compounds that
can be used for photosensitive resin in an embodiment of the
present invention.
[0015] FIG. 5 schematically illustrates additional exemplary
compounds that can be used for photosensitive resin in an
embodiment of the present invention.
[0016] FIGS. 6A and 6B are schematic cross-sectional views
illustrating the exposure step of an embodiment of manufacturing
method according to the present invention;
[0017] FIGS. 7A, 7B, 7C and 7D are schematic cross-sectional views
illustrating an embodiment of manufacturing method according to the
present invention.
[0018] FIG. 8 is a schematic perspective view illustrating an
exemplary configuration of an ink jet recording head.
[0019] FIG. 9 is a schematic plan view illustrating the
configuration of the reticle used in an examination of an
embodiment of the present invention.
[0020] FIG. 10 is a schematic cross-sectional view of ejection of
liquid droplets of a liquid ejection head manufactured by a known
manufacturing method.
[0021] FIGS. 11A and 11B are schematic cross-sectional views
illustrating the exposure step of an embodiment of manufacturing
method according to the present invention.
DESCRIPTION OF THE EMBODIMENTS
[0022] While the aberrations of a lens system can be corrected by
ingeniously devising the lens system as described in Japanese
Patent Application Laid-Open No. 2001-264637, a desired and
accurate lens system can hardly be prepared in a short period of
time. The difficulties that an attempt of preparing such a lens
system encounters are obvious when the process time for meeting the
requirements of the lens system to be used for each product, the
amount of investment for such a novel lens system and the
maintainability of such a lens system are taken into
consideration.
[0023] Meanwhile, for manufacturing a liquid ejection head, there
is a known step of forming ejection ports by exposing the
photosensitive resin film formed on a silicon wafer to light by
means of the stepper of a semiconductor exposure apparatus, using a
reticle 10 having a pattern of ejection ports 13 as illustrated in
FIG. 9 and described earlier. In this process, while the rays of
exposure light that pass through the center and its vicinity of the
projection lens system for exposure to light enter perpendicularly
into the photosensitive resin film, the rays of exposure light 5
that pass through a portion of the projection lens system that is
located near the edge thereof and represent a large curvature in
the semiconductor exposure apparatus are refracted due to
aberrations and enter aslant into the photosensitive resin film
(see FIGS. 1B and 1C). Then, as a result, the rays of light that
are refracted at the edge portion of the lens system strike the
resist (photosensitive resin film) for exposure in directions
inclined from the direction perpendicular to the substrate front
surface (i.e. the surface on which the photosensitive resin film is
formed) so that inclined ejection ports are formed in that portion.
As inclined ejection ports are formed, the printing operation of
the liquid ejection head can be adversely affected by such ejection
ports. Such inclined ejection ports are produced particularly when
a reticle is exploited to near the limits of the angle of view
thereof such as when long chips are manufactured and when a
plurality of chips are arranged side by side for exposure.
[0024] In view of the above-identified problem, the object of the
present invention is to provide a method of manufacturing a liquid
ejection head that can suppress the inclinations of ejection ports
in areas where exposure light enters aslant under the influence the
aberrations of a projection lens system.
[0025] Now, embodiments of the present invention will be described
below by referring to the accompanying drawings. In the following
description given by referring to the accompanying drawings, the
components having the same functions are denoted by the same
reference numerals and will not be described repeatedly in some
instances. While the following description is given in terms of
manufacturing a liquid ejection head of an ink jet recording
apparatus, the description equally applies to manufacturing a chip
or a circuit in a similar manner by means of a semiconductor
exposure apparatus.
[0026] Firstly, an exemplary configuration of an ink jet recording
head to which the present invention is applicable will be
described.
[0027] A liquid ejection head to be manufactured by a method
according to the present invention includes a substrate 1 in which
ejection energy generating elements 8 that generate energy for
ejecting ink are arranged at a predetermined pitch (see FIG. 1C).
An ink supply port for supplying ink to an ink channel is cut
between the two rows of ejection energy generating elements 8,
which may be heater elements, arranged in the surface of the
substrate 1. An ejection port forming member 2 for forming ejection
ports 6 is formed on the front surface (to be referred to merely as
"the surface" in the below) of the substrate by means of a
photosensitive resin layer (see FIG. 1D). The ejection port forming
member 2 includes a plurality of ejection ports 6 that are open at
the tops thereof and arranged above the respective ejection energy
generating elements 8. An ink channel that communicates with ink
supply ports and the ejection ports 6 may also be formed in the
ejection port forming member 2.
[0028] A liquid ejection head is so arranged that the ejection port
surface thereof where a plurality of ejection ports 6 are formed
faces the recording surface of a recording medium (see chip 9 in
FIG. 8). Then, as the pressure generated by the ejection energy
generating elements 8 is applied to the ink filled in the ink
channel by way of the ink supply ports, the liquid ejection head
ejects ink droplets from the ejection ports 6. An image is recorded
as the ejected ink droplets are forced to adhere to the recording
medium.
[0029] Now, an embodiment of method of manufacturing a liquid
ejection head according to the present invention will be described
below.
[0030] With this embodiment of the present invention, an ejection
port forming member for forming ejection ports that eject liquid is
prepared by means of a photosensitive resin layer.
[0031] For example, a channel mold is formed on a substrate 1,
which may be a silicon wafer and in which ejection energy
generating elements 8 such as heater elements are arranged, and
then a photosensitive resin layer is formed so as to cover the
channel mold. Thereafter, an exposure treatment and a development
treatment are conducted on the photosensitive resin layer to
produce an ejection port forming member that has ejection ports
arranged above the respective ejection energy generating elements
8.
[0032] Negative type photosensitive resin may typically be used for
the photosensitive resin layer. Examples of negative type
photosensitive resin that can suitably be used for the purpose of
the present invention will be described hereinafter. Examples of
techniques that can be used for forming the photosensitive resin
layer include spin coating, roll coating and slit coating.
[0033] While a mode of arranging a pattern (channel mold) that
provides a mold of channel is mainly described herein, the use of a
technique that does not use a channel mold is also included in the
present invention.
[0034] If necessary, an ink repellent agent layer may be formed on
the photosensitive resin layer by means of a negative type
photosensitive resist. Examples of application techniques that can
be used for forming an ink repellent agent layer include spin
coating, roll coating and slit coating. When an ink repellent agent
layer is to be provided, the resin of the ink repellent agent layer
and that of the ejection port forming member are preferably not
unnecessarily miscible with each other because the resin of the ink
repellent agent layer is formed on the negative type photosensitive
resin layer while the latter is still unset.
[0035] Then, a dent 3 is formed for each ejection port 6 in a
region including the position for forming the ejection port 6 on
the surface of the photosensitive resin layer (see FIG. 7B). The
dent 3 can be formed by executing an exposure operation and a
baking operation to an extent of not opening the ejection port by
using a reticle or a photomask.
[0036] Now, the step of forming a dent will be described in detail
by referring to FIGS. 7A through 7D. Firstly, a portion of the
photosensitive resin layer that surrounds the position of the dent
3 is exposed to light to an extent of slightly setting that portion
as illustrated in FIG. 7A. The extent of exposure to light at this
time is about 1,500 to 2,500 J/m.sup.2. Thereafter, a dent 3
representing a substantially spherical surface profile as
illustrated in FIG. 7B is produced by baking that portion at about
60 to 120.degree. C.
[0037] The profile and the position of the dent 3 can be
appropriately selected according to the characteristics required to
the liquid ejection head to be manufactured. More specifically, the
profile and the position of the dent can be adjusted by
appropriately defining the shape of the pattern of the mask or the
reticle to be used for forming the dent. Additionally, the depth of
the dent 3 can be adjusted by appropriately selecting the extent of
exposure to light, the temperature and the duration of the heat
treatment or the film thickness of the channel forming member.
[0038] When the dent is cut along a plane perpendicular to the
running direction of the rows of ejection ports, the cross section
of the dent typically represents a circular arc, an elliptic arc, a
catenary or the like. In a plan view of the substrate, or when the
substrate is observed from right above, the dent 3 typically
represents a circular or elliptic boundary line.
[0039] Thereafter, as illustrated in FIG. 7C, the negative type
photosensitive resin layer is subjected to a pattern exposure
operation by way of a mask. Subsequently, as illustrated in FIG.
7D, the negative type photosensitive resin layer is subjected to a
development treatment to produce the ejection port 6. The ejection
port 6 is formed with a taper angle due to the concave lens effect
of the dent 3.
[0040] A photocationic polymerization type epoxy resin composition
is preferably employed for the negative type photosensitive resin
when the mechanical strength of the set resin as structure
material, the ink-resistance of the resin in a recording head, the
resolution and so on are taken into consideration. Particularly
preferable examples of such composition include photocationic
polymerization type epoxy resin compositions based on bis-phenol A
type epoxy resins, phenol novolak type and cresol novolak type
epoxy resins and multi-functional epoxy resins having an
oxycyclohexane skeleton. The epoxy equivalent of any of such epoxy
compounds is preferably not greater than 2,000 and more preferably
not greater than 1,000. This is because an improved crosslink
density is realized at the time of setting reaction and the
obtained photosensitive resin tends to become excellent in terms of
tight adhesion and ink-resistance when the epoxy equivalent is not
greater than 2,000. Examples of photocationic polymerization
initiators that can be used for setting such epoxy resins include
aromatic sulfonium salts and aromatic iodonium salts. Initiators
containing antimony as an anionic component are preferably employed
because such initiators provide an excellent reactivity. Examples
of photocationic polymerization initiators containing antimony
include the compounds expressed by the formulas (1) through (10) in
FIG. 4 and the formulas (11) through (13) in FIG. 5. Photocationic
polymerization initiators containing antimony provide an excellent
polymerization effect relative to epoxy resins and the reaction
products (set products) thereof represent excellent physical
properties. The photosensitive wavelengths that are required to
realize cationic polymerizations are found within a relatively
short wavelength region. For this reason, a relatively high
photosensitivity can be obtained when light with a wavelength not
longer than 300 nm is employed for a patterning operation. In a
photocationic polymerization process of an epoxy resin, cations
(generally protons) deriving from the photocationic polymerization
initiator that is put into the polymerization system are generated
when light is irradiated onto the polymerization system so that a
chain reaction of ring-opening of epoxy groups and polymerization
proceeds. Thus, a polymerization reaction proceeds to a great
extent with a slight quantity of light energy to make the negative
type photosensitive resin extremely highly photosensitive. The
photosensitive wavelengths (the wavelengths that cause reactions
for generating cations to take place) of the photocationic
polymerization initiators illustrated in FIG. 4 are mainly within a
shortwave region not longer than 300 nm. On the other hand, the
compounds illustrated in FIG. 5 have respective photosensitive
wavelengths extending to a relatively long wavelength region.
Therefore, when i rays (365 nm) that are popular in terms of the
wavelengths of exposure apparatus designed for photolithography are
irradiated, the compounds illustrated in FIG. 5 function well as
negative type resists.
[0041] While the method of forming the dent 3 that is currently
being described employs exposure to light and baking, the present
invention is by no means limited to that method and other
appropriate methods can also be used to form dents for the purpose
of the present invention. Examples of such methods include a method
of mechanically applying pressure to the layer for forming
dents.
[0042] The dent 3 can be formed not only by the above-described
method of using a photolithography step, as noted above, but also
by some other method such as an imprint method. Now a technique of
forming a dent 3 by means of an imprint method will be described
below. With an imprint method, a dent pattern can be transferred
onto a negative type photosensitive resin layer by pressing a
molding original plate (to be simply referred to as mold
hereinafter) having a convex pattern that corresponds to the dent
to be transferred against the negative type photosensitive resin
layer. Conditions in which the mold is pressed against the negative
type photosensitive resin layer typically include a mold
temperature range between 20 and 120.degree. C. and a pressure
range between 0.01 and 5 MPa. With a popular imprint method, the
mold is heated to a temperature higher than the glass transition
temperature of the resin onto which the pattern is to be
transferred and the pattern is transferred under pressure of
several MPa. However, in the instance that is being described here,
the aspect ratio of the pattern is small and the dent pattern does
not need to be transferred deep into the negative type
photosensitive resin layer so that the pattern operation can be
conducted at a relatively low temperature with relatively low
pressure. Examples of base materials that can be used for the mold
include various metal materials, glass, ceramic materials, silicon,
quartz, plastic materials and photosensitive resin materials.
[0043] Now, an embodiment of the present invention will be
described in detail by referring to the related drawings.
[0044] As described earlier, a beam of light that has passed
through the projection lens system of a semiconductor exposure
apparatus (e.g., a focusing exposure apparatus for image-size
reducing projection and exposure) near the edge of the system is
refracted toward the center than a beam of light that has passed
through the projection lens system at or near the center of the
system. As the photosensitive resin layer is exposed to such a
refracted beam of light, a latent image of an ejection port is
formed so as to be directed to the direction of the incoming beam
of light. Then, there may be an instance where the formed ejection
port is outwardly directed.
[0045] In view of this possibility, with this embodiment, an
exposure treatment operation for forming a latent image of an
ejection port in a dent 3 using the projection lens system is
conducted such that the center of the top surface of the latent
image is shifted from the lowest point of the dent toward the side
at which a beam of light enters for exposure (see FIG. 2A). In
other words, with this embodiment, a substantially spherical dent
is formed in a region that includes the position at which an
ejection port is to be formed on the surface of a photosensitive
resin layer. Thereafter, a latent image that corresponds to an
ejection port is formed in the dent by means of an exposure
treatment using a projection lens system. In the exposure treatment
operation, the latent image is formed by a beam of exposure light
that are refracted by the projection lens system and inclined from
the direction perpendicular to the substrate surface such that the
center of the top surface of the latent image is shifted from the
lowest point of the dent toward the side from which beam of light
enter for exposure.
[0046] The exposure treatment of this embodiment will be described
in greater detail below by referring to FIGS. 2A through 2D. FIGS.
2A through 2D schematically illustrate the relationship between a
refracted beam of exposure light 5 and the latent image obtained by
means of the beam of exposure light 5. They also illustrate the
positional relationship between the center of the top surface of
the latent image to be obtained and the lowest point 7 of the dent
3. In each of FIGS. 2A through 2C, the arrow of a solid line
indicates the center of the beam of exposure light 5 that enters
the dent.
[0047] With this embodiment, the photosensitive resin layer 2 is
exposed to light such that the center of the beam of exposure light
5 that has been refracted by a projection lens system is shifted
toward the direction of incoming light (the side from which the
beam of exposure light enter the dent 3) relative to the lowest
point 7 of the dent 3. With such an exposure arrangement, the
angles formed by the ejection port lateral surface and the
substrate surface can be made equal to each other at the
transversal opposite ends of the ejection port in a cross section
taken along a plane that passes through the center of the top
surface of the latent image and the lowest point of the dent and
stands perpendicularly relative to the substrate surface.
[0048] Then, an ideal head profile as illustrated in FIG. 1D can be
obtained by conducting an exposure treatment such that the center
of the beam of exposure light 5 (the center of the top surface of
the latent image) that has been refracted by the projection lens
system is shifted toward the direction of the incoming beam of
light relative to the lowest point 7 of the dent so as to make the
angle formed by the ejection port lateral surface and the substrate
surface to be substantially the same at the opposite ends of each
and every one of the ejection ports in a cross section taken along
a plane that passes through the center of the top surface of the
latent image and the lowest point of the dent and stands
perpendicularly relative to the substrate surface so as to extend
in the running direction of the row of ejection ports to which the
ejection port belongs. In other words, the liquid ejection head
that is obtained by means of the above-described exposure
arrangement is such that the directions of the center lines of the
ejection ports are made to be parallel to each other and the
difference in the direction of ejection between the ejection ports
located at and near the center of each row of ejection ports and
those located at and hear the ends of the row is reduced to a large
extent.
[0049] If, on the other hand, the center of the rays of exposure
light and the lowest point 7 of each dent are made to agree with
each other for each ejection port as illustrated in FIG. 2B, the
direction of the center line of an obtained ejection port located
near the edge of the photosensitive resin layer is inclined toward
the direction of the incoming beam of light. Furthermore, if the
center of the top surface of the latent image is shifted relative
to the lowest point 7 of the dent toward the side opposite to the
side of the incoming beam of light, the direction of the center
line of the obtained ejection port is further inclined toward the
direction of the incoming beam of light.
[0050] With this embodiment, the top surface of the latent image is
preferably arranged so as to cover the lowest point of each and
every one of the dents as viewed from right above. If, for example,
the top surface does not cover the lowest point 7 of a dent as
illustrated in FIG. 2D, the ejection port 6 can be inclined toward
the side opposite to the side of the incoming beam of light.
[0051] With this embodiment, the positional relationship between
the center of the dent and the center of the top surface of the
latent image is desirably so adjusted that the angle that is formed
by the lateral surface of the obtained ejection port and the
substrate surface is substantially the same at the opposite ends of
the ejection port in a cross section taken along a plane that
passes through the center of the top surface of the latent image
and the lowest point of the dent and stands perpendicularly
relative to the substrate surface so as to extend in the running
direction of the row of ejection ports to which the ejection port
belongs. The difference of the taper angles at the opposite ends of
the ejection port is preferably less than 0.5 degrees, more
preferably less than 0.3 degrees, most preferably less than 0.1
degrees. When the difference is less than 0.5 degrees, the flying
direction of liquid droplets of the ejection port can be regarded
as being perpendicularly upwardly adjusted relative to the surface
of the photosensitive resin layer if compared with an instance
where no such correcting operation is conducted.
[0052] Now, an embodiment of the present invention will be
described below by referring to FIGS. 1A through 1D.
[0053] FIGS. 1A through 1D schematically illustrate how an exposure
operation is conducted when forming the ejection ports of a liquid
ejection head with this embodiment. More specifically, a
photosensitive resin layer 2 is formed on a substrate 1, which may
be a silicon wafer, and dents 3 are formed on the surface of the
photosensitive resin layer 2. Then, ejection ports 6 are formed in
the respective dents 3.
[0054] Referring to FIG. 1A, a photosensitive resin layer 2 is
formed on the surface of a substrate 1, which may be a silicon
wafer, and a plurality of dents 3 representing a concave profile
are formed and arranged in rows on the surface of the
photosensitive resin layer 2.
[0055] The dents 3 may be so formed that they have a substantially
uniform size in the rows of ejection ports and the gaps separating
adjacent dents 3 may be reduced toward the ends of the rows of
ejection ports. Differently stated, the dents 3 that are located
near the opposite ends of the rows of ejection ports are shifted
inwardly (toward the centers) of the rows. In FIG. 1A, reference
numeral 9 denotes a block that functions as a chip. The substrate
is cut and divided into a plurality of chips in a later step.
[0056] FIG. 1B is an enlarged schematic plan view of a part of a
row of ejection ports (three ejection ports included in an end
region a of a row) as viewed from above.
[0057] FIG. 1C is a schematic cross-sectional view taken along line
1C-1C in FIG. 1B. Note that the lower end of FIG. 1B and the left
end of FIGS. 1C and 1D are located close to one of the opposite
ends of the row of ejection ports.
[0058] In FIGS. 1B through 1D, the following relations hold true
for b, c, d and e, where b and c are the distances between the
centers of adjacently located latent images and d and e are the
distances between the oppositely disposed ends of adjacently
located dents.
b.apprxeq.c,d>e
[0059] In FIGS. 1B through 1D, the centers of the rays of exposure
light 5 for forming ejection ports (the centers of the top surfaces
of the latent images) are separated by equal gaps. Additionally,
the ejection ports 6 of each row of ejection ports are formed to
represent the same positional relationship as the corresponding
ejection energy generating elements 8.
[0060] The positional relationship between the lowest point of the
dent and the center of the top surface of the corresponding latent
image differs from ejection port to ejection port. In other words,
among a plurality of latent images, the center of the top surface
of a latent image is shifted from the lowest point of the dent to a
great extent toward the side of incoming exposure light when the
angle (incident angle) between the direction of the beam of
exposure light striking the dent to form the latent image and the
direction perpendicular to the substrate surface is large. FIG. 1C
illustrates the relationship between the positions of dents and the
beams of exposure light 5 respectively striking the dents and how
the beams of exposure light 5 strike the respective dents. In a row
of ejection ports 6 that are collectively exposed to light, as for
the positional relationship between the lowest point of a dent and
the center of the beam of exposure light for forming an ejection
port there, the lowest point of the dent for forming an ejection
port there is shifted to a great extent toward the center of the
row from the center of the beam of exposure light for forming the
ejection port (the center of the top surface of the latent image
there) when the ejection port 6 is formed at a position located
close to the outside (close to one of the opposite ends of the
row). With such an exposure arrangement, the produced ejection
ports of the row are directed perpendicularly upward (in the
direction perpendicular to the substrate surface) in the row of
ejection ports as illustrated in FIG. 1D due to the refraction
effect of concave lens.
[0061] Now, the present invention will be described further below
by way of examples.
[0062] The following negative type photosensitive resin was
prepared: [0063] epoxy resin: EHPE-3150 (available from Daicel) 120
g [0064] photocationic polymerization initiator: SP-172 (available
from ADEKA) 6 g [0065] intensifier: SP-100 (available from ADEKA)
1.2 g [0066] solvent: methyl isobutyl ketone 100 g
[0067] The above materials were mixed to prepare negative type
photosensitive resin. The negative type photosensitive resin was
applied onto a quartz glass substrate to a film thickness of 1
.mu.m and the absorbance of the negative type photosensitive resin
layer was observed for light having a wavelength of 365 nm to find
out that the absorbance was 0.024.
[0068] Firstly, a silicon substrate having heater elements (heaters
made of material HfB.sub.2) as ejection energy generating elements
and a laminate film (not illustrated) of SiN+Ta at the site for
forming a channel was prepared.
[0069] Then, positive type photosensitive resin (polymethyl
isopropenyl ketone (ODUR: trade name, available from TOKYO OHKA
KOGYO) was applied onto the substrate that includes ejection energy
generating elements 8 by spin coating and baked at 150.degree. C.
for 3 minutes.
[0070] Thereafter, the positive type photosensitive resin was
subjected to a patterning operation to produce a channel mold. More
specifically, a pattern exposure operation was executed with an
exposure dose of 23000 mJ/cm.sup.2 by means of an exposure
apparatus (Deep-UV Exposure Apparatus UX-3000 (tradename) available
from USHIO. Then, a development process was executed by means of
methyl isobutyl ketone and the pattern was subjected to a rinse
treatment, using isopropyl alcohol, to obtain a channel mold having
a channel pattern.
[0071] Subsequently, a negative type photosensitive resin layer 2
was formed on the substrate by applying the prepared negative type
photosensitive resin onto the substrate by spin coating.
[0072] In the example, formation of an ink repellent agent layer
was omitted.
[0073] At this stage, the negative type photosensitive resin layer
2 was subjected to a pre-exposure process and a baking process as
described earlier to form dents 3 in respective regions, each of
which includes the position at which an ejection port is to be
formed on the surface of the photosensitive resin layer 2 (see
FIGS. 7A and 7B).
[0074] Then, the negative type photosensitive resin layer was
exposed to light to form latent images that correspond to
respective ejection ports by means of the technique of this
embodiment (which will be described in detail below) (see FIG. 7C).
In the exposure treatment process, the negative type photosensitive
resin layer was exposed to light with an exposure dose of 1000
J/m.sup.2 by way of a photomask (not illustrated) and by means of
an i rays stepper (available from Canon). Light having a center
wavelength of 365 nm and a half width of 5 nm was used for the
exposure treatment process.
[0075] Thereafter, the negative type photosensitive resin layer was
baked on a hot plate at 90.degree. C. for 180 seconds and then
developed by means of methyl isobutyl ketone. After executing a
rinse treatment process by means of isopropyl alcohol, the resin
layer was subjected to a heat treatment process at 100.degree. C.
for 60 minutes to produce ejection ports 6 (see FIG. 7D).
[0076] Note that the above-described mixing ratio of the materials
for preparing the negative type photosensitive resin is cited only
as an example and the present invention is by no means limited to
it. Additionally, note that formation of an ejection port with a
taper angle due to the concave lens effect of a dent is preferable
for the ejection performance of the ejection port and adopted
because it provides a higher degree of freedom for selecting the
taper angle if compared with an ejection port 6 made to represent a
taper angle by shifting the focus position for defocusing at the
time of exposure to light of the ejection pattern.
[0077] Now, the above-described exposure process for a method of
manufacturing a liquid ejection head will be described below and
Examples of the present invention will also be described in detail
below.
Example 1
[0078] In this example, a 6-inch reticle 10 of a 5-times size
reducing optical system as illustrated in FIG. 6A was used when
forming latent images of ejection ports. The dimensions of the chip
9 to be prepared were such that the chip 9 had a longitudinal
length of 26 mm and a transversal width of 2 mm. In other words,
the length of the chip 9 agrees with the largest angle of view of
the reticle to be used this time, which is 26 mm, so that the
pattern 13 was arranged nearly to the limits of the angle of view
as illustrated in FIG. 9. As for the chip 9, the density of
ejection energy generating elements arranged at each side, or each
row, was 600 dpi and the centers of two adjacently arranged
ejection energy generating elements were separated by about 42
.mu.m. Four dummy nozzles that were not to be used for printing and
four dummy ejection energy generating elements 8 were arranged at
the opposite ends of each row. The photosensitive resin layer 2 had
a thickness of 28 .mu.m and the thickness the orifice plate section
for forming ejection ports 6 (the thickness not including the
thickness of the foam chambers) was 12 .mu.m.
[0079] Each ejection port was designed to have a diameter of 16
.mu.m in order to cause it to eject about 5 pl and each dent 3 was
designed to have a diameter of 35 .mu.m. Firstly, about 4.4
.mu.m-deep dents 3 were formed on the surface of the photosensitive
resin layer 2 by way of exposure to light and baking under the
above-described conditions. At and near the center of each row of
ejection ports, the center of the beam of exposure light for
forming an ejection port that struck the photosensitive resin layer
without being refracted agreed with both the center of the
corresponding dent 3 and that of the ejection port 6. The inverse
taper angle of the ejection port 6 was 2.6 degrees at the opposite
ends in a cross section taken along a plane that passes through the
center of the top surface of the latent image and the lowest point
of the dent and stands perpendicularly relative to the substrate
surface so as to extend in the running direction of the row of
ejection ports to which the ejection port belongs.
[0080] As for each of the ejection ports located at and near the
opposite ends of each row of ejection ports, on the other hand, the
center line of the ejection port becomes parallel to that of an
ejection port located at or near the center of the row to produce
an ideal head profile as illustrated in FIG. 1D when the center of
the beam of exposure light 5 for forming the ejection port is
shifted from the lowest point 7 of the corresponding dent 3 toward
the side from which a beam of light enters for exposure. In other
words, the directions of liquid ejection were made to agree with
each other and a liquid ejection head representing the highest
printing quality can be manufactured when the positional
relationship as illustrated in FIG. 2A is established for the
lowest point of the dent 3 and the center of the ejection port 6
for each of the ejection ports located at and near the opposite
ends of each row of ejection ports.
[0081] A liquid ejection head prepared in a study will be described
below in detail with numerical values of the nozzles that were
actually used for the study. When the beam of incident light was
inclined by 1.0 degree from the direction perpendicular to the
substrate surface and the lowest point 7 of the dent was made to
agree with the center of the rays of light (the center of the top
surface of the latent image to be formed) as illustrated in FIG.
11A (the positional relationship before a correction), the beam of
light was refracted and entered the photosensitive resin layer at
the dent 3. The lateral surface of the obtained ejection port 6 did
not represent the same degree of inclination at the opposite ends
of the lateral surface in a cross section taken along a plane that
passes the center of the top surface of the latent image and the
lowest point of the dent and stands perpendicularly relative to the
substrate surface so as to extend in the running direction of the
row of ejection ports to which the ejection port belongs.
Therefore, the position of the dent 3 was shifted to the direction
opposite to the direction along which the beam of light strikes the
dent 3 relative to the center of the beam of exposure light. As a
result, the taper angle was made equal to 2.6 degrees at the
opposite ends of the lateral surface of the ejection port so that
ejection ports 6 representing a uniform inverse taper angle can be
obtained regardless of the degrees of inclination of the incident
beams of light that were not equal to each other. Thus, ejection
ports could be formed at and near the ends of the rows of ejection
ports so as to be directed perpendicularly upward from the surface
of the photosensitive resin layer just like the ejection ports
formed at and near the center of the rows of ejection ports. The
related values of the prepared samples that were obtained by actual
measurements are listed in Table 1 below.
TABLE-US-00001 TABLE 1 Refraction angle of incident beam of light
(angle of Quantity of shift of inclination of beam center of latent
of light from image surface from Left side direction lowest point
of dent taper angle Right side taper perpendicular to toward
direction of of ejection angle of substrate surface) inclination
port ejection port 0.5.degree. 0.5 .mu.m 2.6.degree. 2.6.degree.
1.0.degree. 1.0 .mu.m 2.6.degree. 2.6.degree. 2.0.degree. 2.0 .mu.m
2.6.degree. 2.6.degree.
[0082] Thus, the present invention provides a method of
manufacturing a liquid ejection head that can suppress the
inclinations of ejection ports in areas where exposure light enters
aslant under the influence the aberrations of a projection lens
system.
[0083] The present invention is applicable not only to ordinary
printing apparatus but also to various apparatus including copying
machines, fax machines having a communication system and word
processors having a printing section as well as to complex
industrial recording apparatus realized in combination with various
processing apparatus.
[0084] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modification and
equivalent structures and functions.
[0085] This application claims the benefit of Japanese Patent
Application No. 2012-164688, filed on Jul. 25, 2012, which is
hereby incorporated by reference herein in its entirety.
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